1. Field of the Disclosure
This disclosure relates generally to moineau motors and pumps used for drilling wellbores.
2. Description of the Related Art
To obtain hydrocarbons such as oil and gas, boreholes or wellbores are drilled by rotating a drill bit attached to a drill string end. A substantial proportion of the current drilling activity involves directional drilling, i.e., drilling deviated and horizontal boreholes, to increase the hydrocarbon production and/or to withdraw additional hydrocarbons from the earth's formations. Modern directional drilling systems generally employ a drill string having a drill bit at the bottom that is rotated by a motor (commonly referred to in the oilfield as the “mud motor” or the “drilling motor”).
Positive displacement motors are commonly used as mud motors. A typical mud motor includes a power section which contains a stator and a rotor disposed in the stator. A stator typically includes a housing that is lined inside with a helically contoured or lobed elastomeric material. The rotor is usually made from a suitable metal, such as steel, and has an outer lobed surface. Pressurized drilling fluid is pumped into a progressive cavity formed between the rotor and stator lobes. The force of the pressurized fluid pumped into the cavity causes the rotor to turn in a planetary-type motion. A suitable shaft connected to the rotor via a flexible coupling compensates for eccentric movement of the rotor. The shaft is coupled to a bearing assembly having a drive shaft, which in turn rotates the drill bit attached thereto.
As noted above, both the rotor and stator are lobed. The rotor and stator lobe profiles are similar, with the rotor having one less lobe than the stator. The difference between the number of lobes on the stator and rotor results in an eccentricity between the axis of rotation of the rotor and the axis of the stator. The lobes and helix angles are designed such that the rotor and stator lobe pair seal at discrete intervals, which creates axial fluid chambers that are filled by the pressurized circulating fluid. The action of the pressurized circulating fluid causes the rotor to rotate and precess within the stator.
The present disclosure provides methods and devices for increasing the reliability, durability, and efficiency of the motors (or pumps), and other similar fluid pressure differential activated devices.